Magnetic translating device



July 25, 1961 R. w. TIBBETTS ETAL 2,994,016

MAGNETIC TRANSLATING DEVICE Filed. Aug. 28, 1957 2 Sheets-Sheet 1 580 ea! 559x922; if WWVW y 1961 R. w. TIBBETTS ETAL 2,994,016

MAGNETIC TRANSLATING DEVICE Filed Aug. 28, 1957 2 Sheets-Sheet 2IZZVBIZJ607ZS f aymrzd W 121680!!! 6607' e 6112x501; ,5? M "W UnitedStates Patent 2,994,016 MAGNETIC TRANSLATIN G DEVICE Raymond W. Tibbettsand George C. Tibbetts, Camden, Maine, assignors to Tibbetts Industries,Inc., Camden, Maine, a corporation of Maine Filed Aug. 28, 1957, Ser.No. 680,765 8 Claims. (Cl. 317-172) The present invention is concernedwith magnetic translating devices having a movable armature, dependingfor operation on variable gaps and variable magnetic fluxes, and therebycapable of translating mechanical to electrical energy or vice versa.

A primary object of the invention is to provide a magnetic transducer inwhich the electrical signal coil is substantially encased in magneticmaterial, with the result that the undesirable sensitivity to straymagnetic fields is greatly reduced.

A further object of the invention is to provide a magnetic translatingdevice in which the magnetically soft portions carrying polarizing fluxmay be minimized in thickness in order to minimize both eddy currentlosses and physical size.

Another object of the invention is to provide a magnetic transducer inwhich the electrical signal coil can readily be located with precision.

Still another object of the invention is to provide a magnetictranslating unit which is highly stable and rugged, and which is compactand structurally complete, enabling it to be applied readily in avariety of complete translating assemblies.

These objects are accomplished in our invention by providing themagnetic portions which carry polarizing flux in such a way that theelectrical signal coil is substantially enclosed, by feeding the gapswith polarizing flux from a large proportion of their peripheries, andby arranging whenever possible for the signal flux and polarizing fluxto be approximately orthogonal in field direction in the greater part ofthe magnetically soft portions that carry both types of flux.

According to this invention the magnetic translating device comprises avibratory armature with means for supporting one part of the armaturewhile leaving another part free to vibrate transversely of apredetermined plane, characterized by magnets extending lengthwise ofthe armature on the opposite sides thereof which are intersected by saidplane, the poles of the magnets being directed transversely of the planein corresponding directions, and sheets of magnetic materialsubstantially bridging the space between the poles of the magnets onopposite sides of the aforesaid plane respectively, the sheetssubstantially covering the armature and presenting pole faces to thevibratory part of the armature.

In a more specific aspect the invention involves means for holding theparts together including a U-shaped clip ;traddling the aforesaid sheetsintermediate the magnets at one end of the device.

For the purpose of illustration typical embodiments of the invention areshown in the accompanying drawlngs in which FIG. 1 is a plan view;

FIG. 2 is a left end view;

FIG. 3 is a side view;

FIG. 4 is a right end view;

FIG. 5 is a section on line 55 of FIG. 3;

FIG. 6 is a section on line 66 of FIG. 1;

FIG. 7 is an isometric view with parts broken away;

FIG. 8 is a section like FIG. 6 showing a modified construction;

FIG. 9 is a plan view of another embodiment;

FIG. 10 is a section on line 1010 of FIG. 9;

FIG. 11 is a right end view of FIG. 9; and

FIG. 12 is an isometric view of the modification with parts broken away.

The particular embodiment of the invention shown in FIGS. 1 to 7comprises a coil 1, which may for example be of the type disclosed andclaimed in the copending application of Raymond W. Tibbetts, Ser. No.681,393, filed August 30, 1957, now Patent No. 2,988,804, issued June20, 1961, an armature 2 extending through the opening 3 in the coil,magnets 6 and '7 extending lengthwise of the armature on the oppositesides of the coil which are intersected by the plane of the armature,the poles of the magnets being directed transversely of the plane incorresponding directions as indicated by the letters N and S in FIGS. 2and 4, and thin sheets 8 and 9 of magnetic material substantiallybridging the space between the poles of the magnets on opposite sides ofthe aforesaid plane respectively. While the coil may be mounted on onesheet only, as by adhesive, as illustrated the sheets are shaped to fitthe coil snugly and hold it in position. At each end the sheets 8 and 9converge toward the armature both laterally and longitudinally tocentral portions which parallel the armature in close juxtapositionthereto. At the right-hand end (FIGS. 1, 3 and 6) non-magnetic spacers11 and 12 are interposed between the sheets and the armature and theparts are secured together by means of a screw 13. At the left-hand endthe armature is free to vibrate between the pole faces 14 and 16 (FIG.6). To transfer vibration to or from the armature a yoke 17 straddlesthe armature and. pinches it snugly therebetween, the yoke extendingoutwardly through an opening 118 in the sheet 8. At its anchored end thearmature has flexible tabs 19 and 20 which may be bent toward one or theother of the sheets 8 and 9 variably to collect magnetic flux, therebyto equalize the flux flowing between the armature and each of the polefaces 14 and 16. The end-s of the coil may be connected to insulatedterminals 21.

In addition to the screw 13 a non-magnetic clip 23 may be slipped overthe central end portions of the sheets 8 and 9 as shown in FIG. 8. Alsothe sheets 8 and 9 may be secured to the magnets 6 and 7, and if desiredalso to the coil 1, by means of a suitable cement such as fluid epoxyresin with an amine type hardener. The clip 23 serves to define thethickness of the air gaps very accurately. Also it does away with thenecessity of extending the pole faces beyond the free end of thearmature for the purpose of securing them together. Thus the length ofthe unit is reduced, this being of prime importance in miniaturedevices.

The modification shown in FIGS. 9 to 12 is similar to that shown inFIGS. 1 to 7 and corresponding parts are correspondingly designated.However instead of the armature being T-shaped it is E-shaped,comprising a central portion 22 corresponding to the part 2 of the firstembodiment, an end portion 23 and side portions 24. Instead of a singlemagnet on each side there are two magnets 26 and 27 on opposite sides ofthe portions 24 of the armature. As in the first embodiment the poles ofthe magnets are directed transversely of the plane of the armature incorresponding directions as indicated by the letters N and S in FIG. 11.Tabs 29 and 30, corresponding to tabs 19 and 20 in the first embodiment,are located on the ends of the portions 24 of the E-shaped armature, themagnets 26 and 27 being shortened to provide a space between the sheets8 and 9 so that each tab may be bent toward either sheet.

As is well known in the art of magnetic transducers, current passingthrough the coil and about the armature causes circulatory signal fluxesthrough the paths defined by the armature and the two sheets 8 and 9.Inasmuch as the signal fluxes have opposite directions in the air gapsbetween the armature and the pole faces 14 and 16.

whereas the polarizing flux supplied by the magnets is in the samedirection in the two gaps, the signal flux increases the total magneticflux in one gap and decreases it in the other gap, so that the armatureis deflected to actuate the yoke 17. In the opposite direction oftransduction the total fiuxes in the two gaps vary oppositely as thearmature is moved back and forth, causing electrical output to beinduced in the coil.

An important feature of the invention consists in that the coil 1 isthroughly shielded from stray magnetic fields by the magnets 6 and 7 andthe sheets 8 and 9. Furthermore the pole faces 14 and 16, and thecorresponding pole faces on the right end (FIGS. 1, 3 and 6), aresupplied with polarizing flux from three sides, that is lengthwise ofthe armature from the inside and crosswise from both sides. Theembodiment shown in FIGS. 1 to 7 has the further advantage that sincethe magnets supply polarizing flux to the sides of the sheets 8 and 9and since the signal flux traverses the sheets in a generally lengthwisedirection, the signal flux and polarizing flux are approximatelyorthogonal in their field directions over the greater part of thesheets, with the exception of the regions near the pole faces and nearthe lengthwise axis of symmetry. This is of significance because apolarizing flux perpendicular in field direction to a signal fluxreduces the incremental permeability of the material for the signal fluxmuch less than the same polarizing flux when superposed on the signalfiux in the same field direction. As a result of these latter twofeatures, the polarizing flux density is minimized in the regions of themagnetic sheets near the gaps, and the eifect of the polarizing fluxupon the incremental permeability of the sheet material for signal fluxis minimized in much of the remainder of the sheets. Therefore thethickness of the sheet material may be considerably reduced as comparedwith conventional designs, resulting in considerably reduced eddycurrent losses and in a smaller unit.

It should be understood that the present disclosure is for the purposeof illustration only and that this invention includes all modificationsand equivalents which fall within the scope of the appended claims.

We claim:

1. A transducer comprising an electromagnetic coil having an openingtherethrough, an armature extending through said opening with a partprojecting from each end of the coil, means for supporting one part, theother part being free to vibrate transversely of a plane containing theaxis of the coil, magnets extending lengthwise of the armature on theopposite sides of the coil which are intersected by said plane, thepoles of the magnets being directed transversely of the plane incorresponding directions, and sheets of magnetic material substantiallybridging the space between the poles of the magnets on opposite sides ofsaid plane respectively, said sheets and magnets substantially enclosingthe coil and having portions projecting beyond the ends of the coil, theprojecting portions extending substantially parallel to the projectingends of the armature so as to present pole faces flatwise to at leastone end of the armature, whereby the coil is thoroughly shielded fromstray magnetic fields and said pole faces are supplied with polarizingflux from three sides.

2. A transducer comprising an electromagnetic coil having an openingtherethrough, an armature extending through said opening with a partprojecting from each end of the coil, means for supporting one part, theother part being free to vibrate transversely of a plane containing theaxis of the coil, magnets extending lengthwise of the armature on theopposite sides of the coil which are intersected by said plane, thepoles of the magnets being directed transversely of the plane incorresponding directions, and sheets of magnetic material substantiallybridging the space between the poles of the magnets on opposite sides ofsaid plane respectively, said sheets locating the coil therebetween andhaving portions projecting beyond the ends of the coil, the projectingportions of the sheets extending in approximately parallel juxtapositionto the projecting ends of the armature so as to present pole facesfiatwise to the armature, whereby the coil is thoroughly shielded fromstray magnetic fields and said pole faces are supplied with polarizingflux from three sides.

3. A transducer comprising an electromagnetic coil having an openingtherethrough, an armature extending through said opening with a partprojecting from each end of the coil, means for supporting one part, theother part being free to vibrate transversely of a plane containing theaxis of the coil, magnets extending lengthwise of the armature on theopposite sides of the coil which are intersected by said plane, thepoles of the magnets being directed transversely of the plane incorresponding directions, and sheets of magnetic material substantiallycovering the coil and armature on opposite sides of said planerespectively, said sheets having portions projecting beyond the ends ofthe coil, the projecting portions of the sheets extending substantiallyparallel to the projecting ends of the armature so as to present polefaces flatwise to at least one end of the armature.

4. A transducer comprising an electromagnetic coil having an openingtherethrough, an armature extending through said opening with a partprojecting from. each end of the coil, means for supporting one part,the other part being free to vibrate transversely of a plane containingthe axis of the coil, magnets extending lengthwise of the armature onthe opposite sides of the coil which are intersected by said plane, thepoles of the magnets being directed transversely of the plane incorresponding directions, and sheets of magnetic material substantiallybridging the space between the poles of the magnets on opposite sides ofsaid plane respectively, said sheets and magnets substantially enclosingthe coil and having portions projecting beyond the ends of the coil, theprojecting portions of the sheets at at least one end of the coil firstconverging towards the armature and thence continuing substantiallyparallel to the projecting ends of the armature so as to present polefaces fiatwise to at least one end of the armature, whereby the coil isthoroughly shielded from stray magnetic fields and said pole facesaresupplied with polarizing flux from three sides, said supporting meansincluding at least one of said sheets.

5. A transducer according to claim 4 further characterized in that saidprojecting portions of the sheets also converge toward each othertransversely from the projecting ends of the magnets toward said polefaces.

6. A transducer comprising an electromagnetic coil having an openingtherethrough, an armature extending through said opening with a partprojecting from each end of the coil, means for supporting one part, theother part being free to vibrate transversely of a plane containing theaxis of the coil, magnets extending lengthwise of the armature on theopposite sides thereof which are intersected by said plane, the poles ofthe magnets being directed transversely of the plane in correspondingdirections, sheets of magnetic material substantially bridging the spacebetween the poles of the magnets on opposite sides of said planermpectively, said sheets su bstantially covering the armature and havingportions projecting beyond the ends of the coil, the projecting portionsof the sheets extending substantially parallel to the projecting ends ofthe armature so as to present pole faces fiatwise to at least one end ofthe armature, and means for securing the parts together including aU-shaped clip straddling said projecting portions of the sheetsintermediate the magnets at one end of the device.

7. A transducer comprising an electromagnetic coil having an openingtherethrough, an E-shaped sheet of magnetic material the middle arm ofwhich extends through said opening with a part projecting from each endof the coil, magnets extending lengthwise of the arms of the sheet andlocated on each side of each of the outside arms of the sheet, themagnets each being polarized transversely of the sheet in the samedirection, and plates of magnetic material substantially bridging thefree poles of the magnets and substantially covering the coil, portionsof the plates projecting beyond the ends of the coil so as to presentpole faces fiatwise to the unattached end of said middle arm, theunattached end of said middle arm being free to vibrate between saidpole faces.

8. A transducer comprising 'an electromagnetic coil having an openingtherethrough, an E-shaped sheet of magnetic material the middle arm ofwhich extends through said opening with a part projecting from each endof the coil, magnets extending lengthwise of the arms of the sheet andlocated on each side of each of the outside arms of the sheet, themagnets each being polarized transversely of the sheet in the samedirection, and plates of magnetic material substantially biidging thetree poles of the magnets and substantially covering the coil, of theplates projecting beyond the ends of the coil, the projecting portionsat one end of the coil first converging towards said middle arm and thenextending substantially parallel thereto so as to present pole facesflatwise to the unattached end thereof, said unattached end being treeto vibrate between said 10 pole faces.

References Cited in the file of this patent UNITED STATES PATENTS 152,433,739 Collins et al Dec. 30, 1947 2,511,114 Lavery June 13, 19502,582,942 Baker Jan. 22, 1952 2,912,523 Knowles et a1 Nov. 10, 1959UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N6.2,994,016 July 25, 1961 Raymond W. Tibbetts et al.

It is hereby certified that error appears in the above numberedpatentrequiring correction and that the said Letters Patent should readas corrected below.

Column 3, line 64, beginning with "2, A transducer" strike out all toand including "sides." in line 8, column 4; columns 4 and 5, for theclaims numbered "'3, 4, 5, 6, 7, and 8;"

read 2, 3, 4, 5, 6 and 7 column 4 line 48, for the claim referencenumeral "4" read 3 in the heading to the printed specification, line 7,for "8 Claims" read 7 Claims Signed and sealed this 23rd day of January1962.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patentsv UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.2,994,016 July 25, 1961 Raymond W, Tihbetts et al.

It is hereby certified that error appears in -the above numberedpetentrequiring correction and that the said Letters Patent should readas "corrected below.-'

Column 8, line 64, beginning with "2 A transducer" strike out all to andincluding "sides." in line 8 column 4; columns 4 and 5, for the claimsnumbered ."3, 4, 5, 6, 7 and 8;" read 2, 3, 4, 5, 6 and 7 column 4, line48, for the claim reference numeral "4" read 3 in the heading to theprinted specification line 7, for "8 Claims' read 7 Claims Signed andsealed this 23rd day of January 1962.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents

